The present invention relates to an autofocus lens apparatus and an camera system including an image-taking apparatus such as a television camera on which the autofocus lens apparatus is mounted.
Lens apparatuses attached to a television camera are generally used in such a manner that a camera operator P places the television camera 1 on his/her shoulder, holds a grip portion 3 provided in a lens barrel 2 of the lens apparatus with his/her right hand, and operates an operation ring rotatably provided on the outer circumference of the lens barrel 2 with his/her left hand, as shown in FIG. 11.
FIG. 11 is a plane view showing a typical lens apparatus. The lens apparatus incorporates a focusing lens unit, a magnification-varying lens unit and an iris, not shown, in its lens barrel 2. The rotational operations of a focus ring 4, a zoom ring 5 and an iris ring 6 which are operation rings provided on the lens barrel 2 enable focusing, varying the magnification and light-amount adjustment, respectively. In the grip portion 3, driving motors, not shown, for electrically driving the operation rings and a controller, not shown, for controlling the driving motors are provided. In addition, on the surface of the grip portion 3, switches which give instructions to the controller are provided such as a zoom operating switch 7, an iris operating switch 8, a return switch 9, and a record switch for instructing start/stop of recording, not shown. These switches are operated by the camera operator with his/her right hand's finger.
When the lens apparatus has an autofocus function, a calculation means, which is provided in the lens apparatus or the television camera, determines the degree of focusing on the basis of image signals from an image-taking region and controls the position of the focusing lens unit via a driving means provided in the lens apparatus, thereby making it possible to obtain an in-focus state automatically.
Even when image-taking is performed with the autofocus lens apparatus, a manual focusing operation of the focus ring 4 with the camera operator's left hand is necessary in cases such as a case where the focus mode is changed quickly from the autofocus mode to the manual focus mode, a case where the camera operator uses the autofocus function as an auxiliary function for manual focusing, a case where the lens apparatus has focused on an object different from the object intended by the camera operator, and a case where the camera operator intends to obtain an out-of-focus state as an image effect.
There are some methods for determining the degree of focusing on the basis of image signals from an image-taking area, such as the so-called contrast detection method and the so-called phase difference detection method. In these methods, the degree of focusing is determined on the basis of image signals from the focus target area in the image-taking region.
When the focus target area is fixed at the center of the image-taking region, the lens apparatus cannot focus on an object away from the center of the image-taking region, which inevitably limits the image-taking condition with a composition in which the object to be focused on is placed at the center of the image-taking region. Therefore, to enable the lens apparatus to focus on an arbitrary object, it would be convenient to change the focus target area in position and size according to the object.
In contrast, a television camera apparatus has been disclosed in, for example, Japanese Patent Laid-Open No. H06(1994)-141226, which is capable of changing the focus target area in position and size according to a camera operator's operation through an operating member provided on a television camera such as a track ball, joystick, touch panel provided in a viewfinder.
Since the camera operator supports the grip portion 3 and operates the plural switches with his/her right hand in image-taking as described above, he/she needs to do the operation for changing the focus target area with his/her left hand. However, since the camera operator needs to absolutely release his/her left hand from the focus ring 4 when he/she does the operation for changing the focus target area in the conventional configuration, it is difficult to take images smoothly in, for example, a case where he/she manually adjusts the degree of focusing.
The use of a command ring as a focus-area-changing ring has been disclosed in Japanese Patent Laid-Open No. 2003-177294. The command ring is rotatable endlessly in the right and left directions and is an item-selecting operation part having a click stop mechanism which temporarily fixes the command ring at each predetermined rotational angular position. Information of rotational directions and rotational amounts (that is, information of the number of exceeded click stops) is send from the command ring to a CPU in the lens apparatus.
According to this configuration, the focus target area can be selected without the absolute release of the camera operator's left hand from the focus ring. However, it is difficult to move the focus target area quickly to a desired position because the selecting operation is an item-selecting operation by the rotation of the command ring.
In particular, in an autofocus lens apparatus mounted on a television camera for taking moving images, the image-taking is continued during the movement of the focus target area. Therefore, there is a problem that a sequential selecting operation of the focus target area is not allowed but a direct movement of the focus target area to a desired position is required.